PIK3CA and gastric cancer: RAS mutations are the most common MAPK alterations observed in human cancer.93 The mutation frequency of KRAS in GC is 6.5%, and PIK3CA is 25%.94,95 Generally, the KRAS mutation is found in intestinal-type tumors whereas the NRAS mutation is reported to appear in diffuse and metastatic GC.96 Using pathway-based gene set enrichment analysis, MAPK/ERK gene features were found elevated in the intestinal subtype of GC.